U.S. patent application number 14/690586 was filed with the patent office on 2016-10-20 for synchronous buck regulator with short circuit to voltage source protection.
The applicant listed for this patent is Continental Automotive Systems, Inc.. Invention is credited to Alfons Fisch, Mikhail Zarkhin.
Application Number | 20160308439 14/690586 |
Document ID | / |
Family ID | 57043765 |
Filed Date | 2016-10-20 |
United States Patent
Application |
20160308439 |
Kind Code |
A1 |
Zarkhin; Mikhail ; et
al. |
October 20, 2016 |
SYNCHRONOUS BUCK REGULATOR WITH SHORT CIRCUIT TO VOLTAGE SOURCE
PROTECTION
Abstract
A method and apparatus for a power converter assembly detects an
over-current, latches off a low-side switch if an over-current is
detected, holds the low-side switch latched off until a PWM
controller provides a predetermined minimum pulse to the latch (for
the duration of the over-current), and unlatches the low-side
switch if a PWM controller provides a predetermined minimum pulse
to the latch. A power converter assembly includes a PWM controller
coupled to the main switch, the PWM controller configured to
control the main switch according to a duty cycle. A latch is
coupled with a secondary switch and configured to selectively turn
off the secondary switch. The PWM controller is configured to
provide a PWM control signal to the latch, and the control signal
is configured to reset the latch to allow the secondary switch to
turn on only when the PWM begins operating with a minimum pulse
width.
Inventors: |
Zarkhin; Mikhail; (West
Bloomfield, MI) ; Fisch; Alfons; (Falkenstein,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Continental Automotive Systems, Inc. |
Auburn Hills |
MI |
US |
|
|
Family ID: |
57043765 |
Appl. No.: |
14/690586 |
Filed: |
April 20, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02M 3/1588 20130101;
Y02B 70/1466 20130101; H02M 3/158 20130101; Y02B 70/10 20130101;
H02M 1/32 20130101 |
International
Class: |
H02M 3/158 20060101
H02M003/158 |
Claims
1. A power converter assembly, comprising: an input node; a main
switch coupled in series with the input node; a pulse-width
modulation (PWM) controller coupled to the main switch, the PWM
controller configured to control the main switch according to a
duty cycle; an inductor coupled in series with the main switch; an
output node coupled in series with the inductor; a secondary switch
coupled in series with the main switch and with the inductor, the
secondary switch coupled to ground; a latch coupled with the
secondary switch and configured to selectively turn off the
secondary switch; and an over-current detector configured to detect
an over-current and to set the latch to turn off the secondary
switch when an over-current is detected, wherein the PWM controller
is configured to provide a PWM control signal to the main switch
and to the latch, the control signal being configured to reset the
latch to turn on the secondary switch, the latch being configured
to remain set after being set by the over-current detector until
the latch receives the control signal from the PWM controller and
is reset by the control signal.
2. The power converter assembly of claim 1, further comprising a
resistor and an input capacitor coupled with the input node, the
resistor and the input capacitor being disposed in parallel with
each other, each of the resistor and the input capacitor being
coupled to ground.
3. The power converter assembly of claim 2, further comprising a
main diode disposed in parallel with the main switch, the main
diode being configured to conduct current toward the input
node.
4. The power converter assembly of claim 3, further comprising a
secondary diode disposed in parallel with the secondary switch, the
secondary diode being configured to conduct current toward the main
switch and the inductor.
5. The power converter assembly of claim 4, further comprising an
output capacitor coupled with the output node and with ground.
6. The power converter assembly of claim 5, the PWM controller
being operable to send the control signal as an input pulse, the
input pulse being operable to turn the main switch ON and OFF.
7. The power converter assembly of claim 6, further comprising a
discriminator disposed in series between the PWM controller and the
latch.
8. The power converter assembly of claim 6, wherein the main switch
is a MOSFET and the secondary switch is a MOSFET.
9. The power converter assembly of claim 8, wherein the power
converter assembly is operable to decrease a DC voltage input to
the output node, the power converter assembly being operable to
output a DC voltage from the output node.
10. A method of protecting against a short circuit to voltage in a
power converter assembly, the method comprising the steps of:
detecting an over-current with an over-current detector; latching
off a low-side switch with a latch if the over-current detector
detects an over-current; holding the low-side switch latched off
until a PWM controller provides a predetermined minimum pulse to
the latch; and unlatching the low-side switch if the PWM controller
provides the predetermined minimum pulse to the latch.
11. The method of claim 10, further comprising providing a DC
current to an input node.
12. The method of claim 11, further comprising providing the PWM
controller as being operable according to duty cycle.
13. The method of claim 12, further comprising providing a
high-side switch in series with the input node and with the PWM
controller, the PWM controller being provided as operable to
control the high-side switch according to the duty cycle.
14. The method of claim 13, further comprising providing an
inductor coupled in series with the high-side switch and an output
node coupled in series with the inductor; the method further
comprising providing the low-side switch as being coupled in series
with the high-side switch and with the inductor; the method further
comprising providing the low-side switch as being coupled to
ground; and the method further comprising providing the latch as
being coupled with the low-side switch.
15. The method of claim 14, further comprising providing a resistor
and an input capacitor coupled with the input node; the method
further comprising providing the resistor and the input capacitor
as being disposed in parallel with each other; the method further
comprising coupling each of the resistor and the input capacitor to
ground; the method further comprising providing a high-side diode
disposed in parallel with the high-side switch; the method further
comprising providing the high-side diode as being configured to
conduct current toward the input node; the method further
comprising providing a low-side diode disposed in parallel with the
low-side switch; the method further comprising providing the
low-side diode as being configured to conduct current toward the
high-side switch and the inductor; and the method further
comprising providing an output capacitor as being coupled with the
output node and with ground.
16. The method of claim 15, further comprising providing a
discriminator disposed in series between the PWM controller and the
latch.
17. A method of protecting against a short circuit to voltage in a
power converter assembly, the method comprising the steps of:
detecting an over-current with an over-current detector; latching
off a low-side switch if the over-current detector detects an
over-current; and keeping the low-side switch latched off for the
duration of the short circuit to voltage.
18. A non-transitory machine-readable medium that provides
instructions, which when executed by a machine, cause the machine
to perform operations comprising: detecting an over-current with an
over-current detector; latching off a low-side switch with a latch
if the over-current detector detects an over-current; holding the
low-side switch latched off until a PWM controller provides a
predetermined minimum pulse to the latch; and unlatching the
low-side switch if the PWM controller provides the predetermined
minimum pulse to the latch.
19. The non-transitory machine-readable medium of claim 18, wherein
the machine is further configured to perform the following
operations: receiving a DC current to an input node, the input node
being coupled with a high-side switch; and operating the PWM
controller according to duty cycle.
Description
FIELD
[0001] This application relates generally to electronic power
systems and, more particularly, to DC-to-DC converter assemblies
and methods.
BACKGROUND
[0002] A power supply is integrated into nearly every electronic
device, both consumer and industrial, including vehicle powertrain
electronics, portable electronic equipment, integrated in-vehicle
systems, computers, medical instrumentation, and many other
devices. Within an electronic device, it may be necessary to either
increase or decrease a voltage by using either a step-up or a
step-down power converter (called a buck or boost). A step-up, or
boost, converter can be used to increase voltage, and a step-down,
or buck, converter can be used to decrease voltage.
[0003] Short circuits of the output voltage node, however, can
cause the power converter assembly not to operate properly. Thus,
short circuit to ground solutions have been implemented by those of
skill in the art.
[0004] In certain conditions, however, the output voltage node may
be shorted to a different voltage rail, or a non-ground, which is
higher than the output voltage and lower than the input voltage and
nevertheless can cause a rise of the input voltage node. This can
damage electronics connected to the input voltage node and/or the
MOSFETs or other switches used in the converter. For example, in a
synchronous buck regulator, the catch diode is replaced by a
low-side switch, the control of which is complimentary to the
high-side switch. Since, unlike the diode, the low-side switch when
turned on can conduct current in both directions, it needs to be
protected in case of the output short circuit to a voltage rail.
This type of failure will cause reverse current into the buck
regulator output, which is only limited by the DC resistance of the
buck inductor. At some point the over-current protection of the low
side switch will turn it off and the current will start to decay.
If this process will repeat over and over, the low-side switch
together with the buck inductor, body diode of the high-side
switch, and the input capacitor will create a boost topology that
will transfer energy from the output to the input. If the
pre-regulator stage feeding the synchronous buck regulator can only
source current and does not have enough loading, then the voltage
at the input capacitor will build up to possibly unsafe higher
levels.
[0005] Accordingly, there is a need for a low-cost and easily
implemented solution for a synchronous buck converter assembly that
is capable of effectively protecting against a short circuit to an
outside voltage source.
SUMMARY OF THE INVENTION
[0006] A power converter assembly is provided that helps protect
against the input capacitor building up unsafe current levels if
the output is shorted to an outside voltage source.
[0007] In one form, which may be combined with or separate from
other forms described herein, a power converter assembly is
provided. The power converter assembly includes an input node, a
main high-side switch coupled in series with the input node, and a
pulse-width modulation (PWM) controller coupled to the main switch.
The PWM controller is configured to control the main switch
according to a duty cycle calculated by the feedback loop. An
inductor is coupled in series with the main switch, and an output
node is coupled in series with the inductor. A secondary low-side
switch is coupled in series with the main switch and with the
inductor. The secondary switch is coupled to ground to provide for
synchronous buck converter architecture and has a short circuit
protection function. A latch is coupled with the secondary switch
and configured to selectively turn off the secondary switch. An
over-current detector is configured to detect an over-current and
to set the latch to turn off the secondary switch when an
over-current is detected. The PWM controller is configured to
provide a PWM control signal to the main switch and to the latch,
wherein the control signal is configured to reset the latch to turn
on the secondary switch, and wherein the latch is configured to
remain set after being set by the over-current detector until the
latch receives the control signal from the PWM controller and is
reset.
[0008] In another form, which may be combined with or separate from
the other forms provided therein, a method of protecting against a
short circuit to voltage in a power converter assembly is provided.
The method includes detecting an over-current with an over-current
detector, latching off a low-side switch if the over-current
detector detects an over-current (using a latch), holding the
low-side switch latched off until a PWM controller provides a
predetermined minimum pulse to the latch, and unlatching the
low-side switch if a PWM controller provides the predetermined
minimum pulse to the latch.
[0009] In yet another form, which may be combined with or separate
from the other forms described herein, a method of protecting
against a short circuit to voltage in a power converter assembly is
provided. The method includes the steps of: detecting an
over-current with an over-current detector; latching off a low-side
switch if the over-current detector detects an over-current; and
keeping the low-side switch latched for the duration of the short
circuit to voltage.
[0010] In still another form, which may be combined with or
separate from the other forms described herein, a non-transitory
machine-readable medium is provided. The non-transitory
machine-readable provides instructions, which when executed by a
machine, cause the machine to perform the following operations:
detecting an over-current with an over-current detector; latching
off a low-side switch with a latch if the over-current detector
detects an over-current; holding the low-side switch latched off
until a PWM controller provides a predetermined minimum pulse to
the latch; and unlatching the low-side switch if a PWM controller
provides a predetermined minimum pulse to the latch.
[0011] These and other features can be best understood from the
following specification and drawings, the following of which is a
brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The following drawings are provided for illustrative
purposes only and are not intended to limit the invention, as
defined in the claims.
[0013] FIG. 1A is a schematic diagram illustrating components of a
power converter assembly, in accordance with the principles of the
present disclosure;
[0014] FIG. 1B is a schematic diagram illustrating components of
another power converter assembly, in accordance with the principles
of the present disclosure;
[0015] FIG. 2 is a block diagram illustrating a method of
protecting against a short circuit to voltage in a power converter
assembly, according to the principles of the present disclosure;
and
[0016] FIG. 3 is a block diagram illustrating a variation of a
method of protecting against a short circuit to voltage in a power
converter assembly, in accordance with the principles of the
present disclosure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] The following description is merely exemplary in nature and
is not intended to limit the present disclosure, application, or
uses.
[0018] Certain terms are used throughout the following description
and claims to refer to particular system components and
configurations. As one skilled in the art will appreciate,
companies may refer to a component by different names. This
document does not intend to distinguish between components that
differ in name but not function. In the following discussion and in
the claims, the terms "including" and "comprising" are used in an
open-ended fashion, and thus should be interpreted to mean
"including, but not limited to . . . ".
[0019] Examples of the invention are described below. It should be
noted that these and other examples or embodiments are exemplary
and are intended to be illustrative of the invention rather than
limiting. While the invention is widely applicable to different
types of systems, it is impossible to include all of the possible
embodiments and contexts of the invention in this disclosure. Upon
reading this disclosure, many alternative embodiments of the
present invention will be apparent to persons of ordinary skill in
the art. Other embodiments may be utilized, and other changes may
be made, without departing from the spirit or scope of the subject
matter presented here.
[0020] With reference to FIG. 1, a power converter assembly for
decreasing a DC voltage is illustrated and generally designated at
10. The power converter assembly 10 is a synchronous buck regulator
configured to step-down the voltage applied to an input of the
power converter assembly 10, according to a duty cycle. With the
normal operation of the power converter assembly 10, a DC voltage
is input into an input node 12 of the power converter assembly 10
and is transformed into a lower DC voltage that is provided through
the output node 14, according to the following equation (in basic
form):
V.sub.OUT=D-Cycle*V.sub.IN,
[0021] where V.sub.IN is the voltage input to the input node 12,
D-Cycle is the duty cycle (which is a positive number always less
than or equal to 1), and V.sub.OUT is the voltage provided from the
output node 14. In some applications, an input voltage of 6 V may
be supplied to the input node 12, by way of example. A capacitor 11
and a resistor 13 are coupled with the input node 12, and the
capacitor 11 and the resistor 13 are disposed in parallel with each
other. Each of the resistor 13 and the input capacitor 11 are
coupled to ground. An output capacitor 15 may be coupled with the
output node 14 and to ground.
[0022] The power converter assembly 10 includes a main switch 16,
or high-side switch, coupled in series with the input node 12. The
main switch 16 may be a transistor, such as a MOSFET. The main
switch 16 may have a main body diode 17 disposed in parallel with
the main switch 16. The main body diode 17 is configured to conduct
current toward the input node 12.
[0023] A pulse-width modulation (PWM) controller 18 coupled to the
main switch 16. The PWM controller 18 is configured to control the
main switch 16 ON and OFF according to a duty cycle calculated by a
feedback loop.
[0024] An inductor 20, or an inductive winding, is coupled in
series with the main switch 16. When the main switch 16 is open, or
off, no current will flow from the input node 12 to the inductor
20. When the main switch 16 is closed (on), however, current will
begin to increase and to flow to the inductor 20. The inductor 20
will produce an opposing voltage across its terminals in response
to the changing current. This voltage drop counteracts the voltage
of the source, reducing the net voltage. Over time, the inductor 20
will store energy in the form of a magnetic field. The inductor 20
is coupled in series with the output node 14.
[0025] A secondary switch 22, or low-side switch, is coupled in
series with the main switch 16 and with the inductor 20. As shown,
the secondary switch 22 is coupled to ground. The secondary switch
22 may have a secondary body diode 23 disposed in parallel with the
secondary switch 22. The secondary body diode 23 is configured to
conduct current toward the main switch 16 and the inductor 20.
[0026] When the main switch 16 is open (off), the secondary switch
22 will normally be closed (on), and vice versa; in other words,
the main switch 16 and the secondary switch 22 are out of phase
with each other. When the main switch 16 is open, current will
continue to flow through the inductor 20, output node 14, buck
converter load and return through ground and through the closed
secondary switch 22. The inductor 20 then discharges energy stored
in magnetic field into the load at the output.
[0027] Current can flow in both directions through the secondary
switch 22 when it is closed. Accordingly, in a situation where the
output node 14 is shorted to a voltage rail, such as, e.g., a 1.2 V
or a 3.3 V nearby voltage rail, energy may be supplied from that
voltage rail back to the input node 12. In such a situation,
without the improvements described below, the power converter
assembly 10 would become a boost power converter in the opposite
direction where a higher voltage would be supplied back to the
input capacitor 11 and the input node 12. The current in the input
capacitor 11 could then rise to unsafe levels and damage
electronics connected to the input node 12.
[0028] Accordingly, when the output node 14 is shorted to a voltage
that is in between the desired input and output voltages
(V.sub.OUT<V.sub.SHORT<V.sub.IN), components of the present
power converter 10 protect against the situation described above,
where components may see a rise in current to unsafe levels. A
latch 24 is coupled with the secondary switch 22 and is configured
to selectively turn off the secondary switch 24. An over-current
detector 26 is configured to detect an over-current coming through
the secondary switch 22 and to set the latch 24 to turn off the
secondary switch 22 when an over-current is detected. Therefore,
the latch 24 will override the normal complimentary nature of the
main switch 16 and the secondary switch 22, because in an
over-current situation, both the main switch 16 and the secondary
switch 22 may be off, or open.
[0029] The latch 24 is configured to remain set for the duration of
the voltage short, and therefore, to keep the secondary switch 22
latched open. The PWM controller 18 is configured to provide the
PWM control signal to the latch 24 (at the same time as it provides
the PWM control signal to the main switch 16). The PWM control
signal is configured to reset the latch 24 to close and turn on the
secondary switch 22. Thus, the latch 24 is configured to remain set
after being set by the over-current detector 26 until the latch 24
receives the control signal from the PWM controller 18 and is
reset. If the voltage exceeds the desired output voltage, however,
no PWM signal will be sent from the PWM controller 18 to the main
switch 16 or the latch 24. Accordingly, no reset of the latch 24
will occur until the PWM control signal is sent.
[0030] For example, when the fault condition is removed, the output
capacitor 15 will naturally discharge and at some point in time,
the output voltage will drop. After the output voltage drops, the
control loop will resume the operation of the main switch 16. At
that particular moment, the latch 24 will be reset and the
secondary switch 22 will then close after the main switch 16
reopens. Accordingly, no reset of the latch 24 will occur until it
is safe to re-close the secondary switch 22, which is only after
the main switch 16 is closed and then opened.
[0031] Referring now to FIG. 1B, a variation of a power converter
assembly is illustrated and generally designated at 10b. The power
converter assembly 10b has similar components to the power
converter assembly 10, such as an input node 12, a resistor 13, an
input capacitor 11, a main switch 16, a main body diode 17, an
inductor 20, an output node 14, an output capacitor 15, a secondary
switch 22, a secondary body diode 23, a latch 24, and an
over-current detector 26. These components may be the same as
described above with respect to FIG. 1A.
[0032] The power converter assembly 10b has a PWM controller 18b,
which is similar to the PWM controller 18, except that the PWM
controller 18b has a minimum duty cycle, in that it is always
running at some non-zero minimum duty cycle. Therefore, to prevent
the latch 24 from being reset by the minimum duty cycle, a
discriminator 28 is disposed in series between the PWM controller
18b and the latch 24. The discriminator 28 prevents very short
pulses associated with the minimum duty cycle from resetting the
latch 24. Accordingly, the latch 24 will only be reset when the
power converter assembly 10b is operating normally and there is no
short to a non-zero voltage.
[0033] Referring now to FIG. 2, a method of protecting against a
short circuit to voltage in a power converter assembly is
illustrated and generally designated at 100. The method 100 may be
used with one of the power converter assemblies 10, 10b illustrated
and described above, though the method 100 need not necessarily use
the power converter assemblies 10, 10b.
[0034] The method 100 includes a step 112 of detecting an
over-current with an over-current detector, such as the
over-current detector 26. The method 100 includes another step 114
of latching off a low-side switch if the over-current detector
detects an over-current with a latch. For example, the latch 24 may
be used to latch off the low-side switch 22. The method 100 further
includes a step 116 of holding the low-side switch latched off
until a PWM controller provides a predetermined minimum pulse to
the latch. Finally, the method 100 includes unlatching the low-side
switch if a PWM controller provides a predetermined minimum pulse
to the latch. This may be any minimum pulse, such as described with
respect to FIG. 1A, or a minimum pulse that is above the minimum
pulse of the PWM controller, such as described with respect to FIG.
1B.
[0035] The method 100 may include additional steps, such as
providing a DC current to an input node, as described above. The
method 100 may also include providing the PWM controller as being
operable according to duty cycle. The method may further include
providing a high-side switch in series with the input node and with
the PWM controller, the PWM controller being provided as operable
to control the high-side switch according to the duty cycle.
[0036] In addition, the method 100 may include providing other
components, such as those shown and described with respect to FIG.
1A. For example, the method 100 may include providing an inductor
coupled in series with the high-side switch and an output node
coupled in series with the inductor; providing the low-side switch
as being coupled in series with the high-side switch and with the
inductor; providing the low-side switch as being coupled to ground;
and providing the latch as being coupled with the low-side switch.
Also, the method 100 may include providing a resistor and an input
capacitor coupled with the input node; providing the resistor and
the input capacitor as being disposed in parallel with each other;
coupling each of the resistor and the input capacitor to ground;
providing a high-side diode disposed in parallel with the high-side
switch; providing the high-side diode as being configured to
conduct current toward the input node; providing a low-side diode
disposed in parallel with the low-side switch; providing the
low-side diode as being configured to conduct current toward the
high-side switch and the inductor; and providing an output
capacitor as being coupled with the output node and with ground. In
some variations, the method 100 may also include providing a
discriminator disposed in series between the PWM controller and the
latch.
[0037] Referring now to FIG. 3, a variation of a method of
protecting against a short circuit to voltage in a power converter
assembly is illustrated and generally designated at 200. The method
200 includes a step 212 of detecting an over-current with an
over-current detector. The method 200 also includes a step 214 of
latching off a low-side switch if the over-current detector detects
an over-current. The method 200 then includes a step 216 of keeping
the low-side switch latched for the duration of the short circuit
to voltage. This may be accomplished, for example, as described
above by resetting the latch 24 only with a minimum PWM control
signal. Other steps of the method 200 may be similar to those
described above with respect to the method 100 or the apparatuses
10, 10b.
[0038] In some variations, a non-transitory machine-readable medium
is used that provides instructions, which when executed by a
machine, cause the machine to perform operations. These operations
may include the steps of one of the methods 100, 200, such as:
detecting an over-current with an over-current detector; latching
off a low-side switch with a latch if the over-current detector
detects an over-current; holding the low-side switch latched off
until a PWM controller provides a predetermined minimum pulse to
the latch; and unlatching the low-side switch if the PWM controller
provides a predetermined minimum pulse to the latch, by way of
example. The machine may be further configured to perform the
operations of receiving a DC current to an input node, the input
node being coupled with a high-side switch, and operating the PWM
controller according to duty cycle.
[0039] Although embodiments of this invention have been disclosed,
a worker of ordinary skill in this art would recognize that certain
modifications would come within the scope of this invention. For
that reason, the following claims should be studied to determine
the true scope and content of this invention.
* * * * *